Method and apparatus for detecting vehicle wheels

Abstract

Method for detecting wheels of a vehicle that is traveling on a roadway in a travel direction and the wheels of which are at least partially exposed laterally. The method including: emitting an electromagnetic measurement beam lobe with a known temporal progression of frequency from the side of the roadway onto an area of the roadway and at a slant with respect to the travel direction, receiving the measurement beam lobe reflected by a passing vehicle and recording the temporal progression, relative to the known progression, of all of its frequencies, and during the passage of a vehicle, detecting a frequency spread appearing in the recorded progression and exceeding a predetermined spread magnitude, as a wheel.

What is claimed is: 
     
       1. A method for detecting a wheel of a vehicle that is traveling on a roadway in a travel direction, the wheels of which are at least partially exposed laterally, the method comprising:
 emitting, from a Doppler lidar or radar device, an electromagnetic measurement beam lobe having a known temporal progression of frequency, from the side of the roadway onto an area above the roadway and at a slant with respect to the travel direction; 
 receiving the measurement beam lobe reflected by a passing vehicle and recording the temporal progression, relative to the known progression, of all of its frequencies appearing at the same time as a reception frequency mixture in the device; and 
 during the passage of the vehicle, detecting, in an evaluation unit, a frequency spread appearing in the recorded temporal progression of the reception frequency mixture and exceeding a predetermined threshold value, as a wheel. 
 
     
     
       2. The method according to  claim 1 , wherein the predetermined threshold value is determined in a previous step from a frequency spread that occurs during the passage of a wheel-less part of the vehicle. 
     
     
       3. An apparatus for detecting a wheel of a vehicle that is traveling on a roadway in a travel direction, the wheels of which are at least partially exposed laterally, comprising:
 at least one Doppler lidar or radar device that is configured to emit an electromagnetic measurement beam lobe with a known temporal progression of frequency onto a target and record the temporal progression, relative to the known progression, of all frequencies occurring at the same time from the measurement beam lobe reflected by the target, as a reception frequency mixture, 
 wherein the measurement beam lobe is oriented from a side of the roadway onto an area above the roadway and at a slant with respect to the travel direction, and 
 a downstream evaluation unit configured to detect a frequency spread appearing in the recorded temporal progression of the reception frequency mixture during the passage of the vehicle and exceeding a predetermined threshold value, as a wheel. 
 
     
     
       4. The apparatus according to  claim 3  comprising a Doppler radar device, wherein the Doppler radar device is constituted by a roadside WLAN, WAVE, or DSRC radio beacon.